The present disclosure relates to an assembly that disengages a pin assembly of a tandem, and in particular, to an assembly that attaches to the tandem and maintains the tandem in a disengaged position from a truck trailer while the truck trailer undergoes positioning over the tandem for load adjustments.
In the trucking and heavy equipment industry, particularly in the tractor-trailer vehicle industry, loads of various sizes and weights must be handled. While handling these loads, trailer operators/drivers must comply with specific laws governing the permissible weight of trailers that travel on freeways and highways. Typically, the laws specify the maximum allowable weight per tandem of the trailer.
In most tractor-trailer vehicles, the trailers connect with the tandem, so called because this unit usually contains two axles and associated wheels. The tandem also contains the suspension system and brakes for the trailer. These tandems can be moved longitudinally along the length of the trailer to provide stability when loading and/or to distribute the weight of the load during transport. The tandem mounts on an underside of a trailer chassis, and is movable longitudinally there along to provide a means of variable load distribution. As noted, the amount of cargo that a trailer carries is governed by local, state and/or national road and bridge laws, and is dependent on proper load distribution. Proper placement of the tandem varies individual axle loads or redistributes the trailer load so that the trailer load is within legal limits.
Once the operator properly positions the tandem for the load, a retractable pin assembly connects the tandem to the trailer chassis. This retractable pin assembly generally includes two or more, and typically four, retractable pins that may be operated by a lever mechanism. When the pins are in their extended position, the pins extend through a corresponding opening formed in the tandem and selectively engage one of a plurality of openings formed in the trailer chassis. The pins, in the engaged position, lock the tandem in a selected position relative to the trailer chassis. To disengage the pins, the operator pulls a handle of the lever mechanism, known as a “pull rod”, wherein the pull rod pivots the pins out of the openings of the trailer chassis so that the tandem disengages from the trailer.
Operators of tractor-trailer trailers must frequently change the position of the tandem axels relative to the trailer to comply with the particular trailer weight laws. Several changes may be required during a single trip where the load is sequentially reduced. When the operator wants to change the positioning of the tandems, the operator performs a series of steps. With the trailer held in position by chocks or brakes, the operator manipulates the pull rod to pull the pins out of their corresponding openings. The operator then stabilizes the tandem and enters the cab to move the trailer to the required position over the tandem.
During these movements, the operator enters the cab and inches the trailer forward or backward while maintaining the tandem axels in the same place. The operator, while in the cab, guesses as to how much movement of the trailer will result in the desired amount of relative trailer movement for proper load distribution. After making an initial guess, the operator exits the cab to observe the actual amount of trailer movement, and then reenters the cab to make further adjustments. These adjustments are known as “bumping” the trailer. Once the operator achieves the desired position, the pins must be reseated into the trailer. This reseating requires that the operator move the pull rod so that the pins move back into the engaged position, following which the operator again gets into the cab and slowly moves the trailer until the pins slide into their corresponding openings and once again lock the trailer and tandem together. Finally, the operator normally walks back to check that all pins are securely in place.
During trailer movement, however, the pins may become jammed due to corrosion, age, rust and worn parts and will bind the pins in the engaged position. The trailer must be moved slightly or rocked back and forth to center the pins in the specific openings. This position must be found by the operator by trial and error, with each attempt necessitating trips from near the back of the trailer to the cab. With use of longer trailers, combined with the fact that the operator may be doing this in extreme weather conditions, adds to the potential for this trailer movement being a very frustrating, time-consuming and dangerous task.
Since the pull rod must be maintained in the disengaged position during the trailer movement, the operator must make numerous trips in and out of the cab to repeatedly pull the pull rod to disengage any jammed pins. When the operator pulls the pull rod, enough force must be applied to overcome spring loading of a return spring, and to hold the pins in an unlocked position. Typically, the operator grasps the handle and yanks the pull rod toward the operator's shoulders. Thus, when the pins become jammed, the operator of the trailer risks personal injury due to overexertion in attempting to manually free jammed pins.
A typical method of attempting to release jammed pin mechanisms involves the operator to rock the trailer fore and aft, while an assistant manually operates the retractable pin assembly via the pull rod. The rocking motion briefly realigns the misaligned openings, so that the assistant can retract the pins during the period of realignment. The assistant's position next to the moving trailer, however, leads to an injury risk since the assistant is concentrating on handling the pull rod and is not concentrating on the moving trailer.
Various release tools assist in pulling the pins in the disengaged position, wherein these tools generally allow the trailer operator to maneuver the trailer while the release tools frees the jammed pins, thus effectively obviating the need for another person to manually operate the release mechanism. During use, one end of the typical release tool attaches to the trailer itself, which will be moving in relation to the pull rod to which the other end of the tool is attached. If a large adjustment of the trailer over the tandem is to be made, the operator must repeatedly walk back to the tandem and disconnect the tool from the trailer. The operator needs to disconnect the tool from the trailer during large adjustments, as the length of the trailer movement will break the tool if the tool remains connected to the trailer. Once the trailer position is adjusted, the operator makes another trip back to the tandem to release the pull rod.
Additionally, the current release tools are portable assemblies requiring that the operator: assemble the tool, attach the respective tool ends to the pull rod and to the trailer and disassemble the tool for storage. These multiple steps results in labor inefficiencies. Given these problems, a tandem assembly to help the operators in adjusting loads is desirable. The assembly needs to be attached to the tandem while remaining free from contact with the trailer. Further, the assembly needs to be attached to the tandem such that after initial set up, the assembly can be repeatedly used without disassembly from the tandem. In other words, the assembly remains on the tandem as the operator drives the trailer to its destination. Additionally, the assembly must be adjustable for different types of trailers with a minimum amount of trouble, while being adaptable for older trailers where the pull rod may be bent out of shape due to improper handling.